xci: Move sourcing of configuration files to the install-lib.sh

xci: Move sourcing of configuration files to the install-lib.sh

The install-lib.sh assumes that certain configuration files have been
loaded before it's sourced. However, this doesn't work well when other
scripts are using install-lib.sh directly since they also need to load
the same configuration files. As such, lets source all these
configuration files from the install-lib.sh file directly. We also
rename this file to 'xci-lib.sh' since it's not just about installation
helpers anymore.

Change-Id: I35e1e804db06b2bb512e4991e5fdf21a72ffaadb
Signed-off-by: Markos Chandras <mchandras@suse.de>